Cognitive Radio (CR) is a novel wireless communication technology that allows for adaptive configuration of the reception parameters of a terminal, based on the information collected from the environment. Cognitive radio (CR) technology can be used in innovative spectrum management approaches like spectrum sharing, where radio frequency spectral bands can be shared among various users through a dynamic exclusive-use spectrum access model. Spectrum sharing can be applied to various scenarios in the commercial, public safety and military domain. In some scenarios, spectrum sharing demands a mechanism for expressing and enforcing access control policies for the allocation of resources including spectral bands. The access control polices should state what are the available resources (e.g. transmission/reception bandwidths), what are the users that are allowed to access them and under what conditions. However, due to the intrinsically highly dynamic nature of specific scenarios (e.g., public safety, military), where parties with various levels of authority may suddenly appear, it may be difficult to establish in advance what are the most suitable access control policies. Trust negotiation is a well-known approach for expressing and enforcing distributed access control policies which depend on two or more parties. In this work we present a trust negotiation-based framework, which allows for the definition of highly expressive and flexible distributed access control policies for the allocation of spectrum resources. Copyright c 2011 John Wiley & Sons, Ltd.